How do you replace a file in fine manager in ee3? I cant believe this is not possible, there must be a way. :/
Hard to believe, but it is not possible to replace a file, You can only remove a file and add new file.
If you want to replace the file without EE file manager, You can access server via FTP s/w like filezilla and replace the image from your image path. That's the only solution of replace the file.